Host–Guest Recognition Boosts Biomimetic Mono/Multivalent Cation Separation
Weisheng Yu, Chengpeng Wei, Kaiyu Zhang, Jianjun Zhang, Zijuan Ge, Xian Liang, Michael D. Guiver, Xiaolin Ge, Liang Wu, Tongwen Xu
Abstract
Biomimetic ion permselective membranes with ultrahigh ion permeability and selectivity represent a research frontier in ion separation, yet the successful fabrication of such membranes remains a formidable challenge. Here, we demonstrate a 4-sulfocalix[4]arene (4-SCA)-modified graphene oxide (GO) membrane that shows extraordinary performance in separating mono-from multivalent cations, as well as having reversible pH-responsiveness. The resulting 4-SCA-modified GO (SCA-GO) membrane preferentially transports potassium ions (K + ) over radionuclide cations (Co 2+, UO 2 2+, La 3+, Eu 3+, and Th 4+ ). The ion selectivities are an order of magnitude higher than that of the unmodified GO membrane. Theoretical calculations and experimental investigations demonstrate that the much-improved ion selectivity arises from the specific recognition between 4-SCA and radionuclide cations. The transport of multivalent radionuclides is impeded by a binding–obstructing mechanism from the host–guest interactions. Interestingly, the host–guest interactions are responsive to the protonation/deprotonation transformation of the 4-SCA. Therefore, the SCA-GO membrane mimics pH-regulated ion selective behavior found in biological ion channels. Our strategy of designing a biomimetic permselective GO membrane may allow efficient nuclear wastewater treatment and, more importantly, deepen our understanding of biomimetic ion transport mechanisms.